Vehicle brake and sanding apparatus



April 23, 1940. c. c. FARMER VEHICLE BRAKE AND SANDING APPARATUS on no mm #0 no N? Original Filed July 29, 1938 m9 wm 03 m VQ l INVENTOR CLYDE C. FARMER ATTORNEY Patented Apr. 23, 1940 PATENT OFFICE VEHICLE BRAKE AND SANDING APPARATUS Clyde 0. Farmer, Pittsburgh, Pa, assignor to The Westinghouse Air Brake Company, Wilmer-ding, 'Pa., a corporation of Pennsylvania Original application July 29, 1938, Serial No.

Glaims.

This invention relates to vehicle brake and sanding apparatus, particularly brake and sanding apparatus controlled automatically by variations in the rotative condition of a vehicle wheel as when slipping,- and is a division of my prior copending application Serial No. 221,951, filed July 29, 1938.

As is well known, when the brakes associated with a vehicle wheel are applied with suiiicient force to exceed the limit of adhesion-between the tread or rim of the wheel and the road or rail surface, the wheel rapidly decelerates toward a locked ornon-rotative condition. ing force on a slipping vehicle wheel is rapidly reduced at the instant the wheel begins to slip, the vehicle wheel will cease to decelerate and accelerate back toward a rotative speed corresponding to vehicle or rail speed without actually reaching the locked or non-rotative condition.

For convenience, the term slip or slipping is applied herein to the rotation of a vehicle wheel at a speed less than a rotative speed corresponding to vehicle or rail speed at a given instant, whether the wheel is decelerating or ac-,- celerating.

The term slide or sliding is employed herein to designate the dragging of the vehicle wheel along a road surface or rail in a locked or non-rotative state. Thus it should be understood that a slipping wheel is one that is rotating whereas a sliding wheel is one that is not rotating.

If the brakes on a slipping wheel are reapplied while the wheel is accelerating back toward vehicle or rail speed following the automatic release of the brakes and a sufficient degree of application is attained, the wheel may again decelerate toward a. locked or non-rotative state. In order to prevent, as much as possible, repeated slipping cycles, it is desirable to avoid reapplying the brakes on a slipping wheel until it returns fullyto a speed corresponding to vehicle speed. For the same reason, it is also desirable not to restore the original degree of application of the brakes which initiates slipping of a wheel.

In my prior copending application, Serial No. 209,648, filed May 24, 1938, and assigned to the assignee of this application, there is disclosed an equipment for effecting the above desirable objectives. In my prior application, Serial No. 209,648, an arrangement is provided whereby reapplication of the brakes on a wheel following slipping thereof is controlled automatically by brake cylinder pressure so as to insure prevention of reapplication 'of the brakes until the brake cylinder pressure has reduced below a predeter- Divided and this application ary 18, 1939, Serial No. 257,126

If the brak- Febru- .prior application also discloses an arrangement which is normally ineffective to restrict the rate of supply of fluid under pressure to a brake cylinder and which is automatically conditioned when 'avehicle wheel slips so as to restrict the rate of resuppl'y to the brake cylinder effected I after the slipping wheel returns fully to the vehicle or rail speed.

My present invention is adapted to accomplish the same desirable objectives as the arrangement disclosed in my prior application but by simplifled and improved means.

It is possible that even with controlled reapplication of the brakes following a slipping wheel condition, recurrence of wheel slipping may occur in cases where the adhesion or rolling friction between a vehicle wheel and the'rail is very low. In order therefore, to further insure against recurrent slipping cycles, my invention further includes an arrangement for automatically effecting sanding of the rails, and a consequent improvement in the adhesion between the wheel and the rail, upon initiation of slipping of a wheel and for automatically terminating the sanding after a predetermined lapse of time.

My invention includes a control valvemechanism of novel construction adapted to effect the release of the brakes .in response to a wheel slipping condition, to prevent reapplication'of the brakes until the brake cylinder pressure reduces below a certain uniform low pressure, to control the rate of re'application, and to control automatic sanding of the rails.

It is accordingly the primary object of my present invention to provide vehicle brake and sanding apparatus including means operative automatically at the instant a vehicle wheel slips for effecting sanding of the road or rail surface.

Another object of my invention is to provide vehicle brakeand sanding apparatus of the character indicated in the foregoing object and further adapted to automatically terminate the sanding operation at the expiraton oi a certain limited length of time following the initiation of slipping of the vehicle wheel. A further object of my invention is to provide a-control valve mechanism of novel construction adapted to control the sanding of the road surface or rails in response to the slipping of a vehicle wheel.

The above objects, and other objects 'of my invention which will be made apparent hereinafter, are attained by means of an embodiment of my invention subsequently to be described and shown in the single figure of the accompanying drawing.

Description of equipment The equipment comprising one embodiment of my invention, as shown in the single figure in the accompanying drawing, includes one or more brake cylinders II for effecting application and release of the brakes associated with an individual wheel and axle unit or a plurality of wheel and axle units, not shown, a source of fluid under pressure hereinafter called the main reservoir I2, a manually operable self-lapping brake valve l3, a straight-air pipe [4 the pressure in which is controlled by the brake valve |3, a brake cylinder pipe I5 through which fluid under pressure is supplied from the straight-air pipe l4 to the brake cylinder II, a control valve mechanism I6 interposed in the brake cylinder pipe l5 and controlled by a magnet valve device I! and a Wheel-slip responsive device N3 of the rotary inertia type associated with the same wheel and axle unit as is the brake cylinder The equipment further comprises a pressure operated switch IS, a plurality of sanding devices 2|, a sanding reservoir 22, a sanding control valve device 23 and a timing reservoir 24 for timing the operation of the sanding control valve device 23.

Considering the parts of the equipment in greater detail, the brake valve I3 is of the type described and claimed in Patent No. 2,042,112 of Ewing K. Lynn and Rankin J. Bush. In view of the detailed description given in the patent, a functional description of the brake valve I3 is deemed sufiicient for the purposes of the present application. When the operating handle 25 of the brake valve I3 is in its normal release position, the brake valve is conditioned to vent the straight-air pipe M to atmosphere. When the handle 25 is shifted horizontally out of its normal release position into a so-called application zone, the brake valve is conditioned to establish communication through which fluid under pressure is supplied from a supply pipe 23, connected to the main reservoir l2, to the straight-air pipe M, the brake valve being automatically selflapping to establish a pressure in the straightair pipe |4 substantially proportionate to the displacement of the operating handle 25 out of its normal release position.

Should the pressure in the straight-air pipe l4 tend to reduce due to leakage or for other reasons, .from a pressure corresponding to the position of the operating handle, the brake valve is automatically operative to supply further fluid under pressure to the straight-air pipe to restore and maintain a pressure therein corresponding to the position of the brake valve handle. This pressure maintaining feature of the brake valve |3 is of importance in connection with the reapplication of the brakes as will be described hereinafter. It should be understood that the straight-air pipe l4 comprises pipe sections car ried respectively on all cars of a train and connected through suitable hose couplings between the cars in conventional manner.

The control valve mechanism 6 comprises a casing having a main section 3| and two end or cover sections 32 and 33, respectively, adapted to be secured to the main section 3| in sealed relation by gaskets 33a and 33b, and suitable screws or bolts, not shown. Embodied in the casing of the control valve mechanism l6 are a release and reapplication valve device 34 hereinafter referred to as the release valve device, and valve device 35 for controlling the rate of resupply of fluid under pressure to the brake cylinder and hereinafter referred to as the reapplication control device.

The release valve device 34 comprises an annular piston 37 having a tubular stem 38, extending to one side thereof, the outer end of which is closed and formed as a piston valve 39, hereinafter designated the vent valve. Also formed on the outside of the hollow stem 38 at a point between the vent valve 39 and the piston 31 is a piston 4|. bore 42 formed in the casing section 3| while the vent valve 33 and piston 4| operate in a bore 43 of smaller diameter than the bore 42 and in c0- axial alignment therewith.

The bore 42 opens at the face of the casing section 3| covered by the end section 32, a chamber 44 being thus formed between the piston 31 and the casing section 32 at the upper side of the piston 37. Interposed between the end casing section 32 and the piston 37 within chamber 44 is a coil spring 45, one end of which engages in a suitable recess 46 in the casing section 32 and the other end of which is received in and bears against the closed end of the hollow stem 38 of the piston 31. The spring 45 normally yieldingly urges the piston 37 downwardly to effect seating of the vent valve 39 on an annular rib seat 4'! which surrounds an exhaust port 48. An annular gasket 43 is inset in the face of the vent valve 39 for eifec'ting sealing engagement with,

the annular rib seat 41.

Formed in the casing section 3|, between the pistons 3'5 and 4| of the release valve device 34 and in surrounding relation to the stem 38, is an annular chamber 5| to which the brake cylinder II is connected through a passage 52 and one section of the brake cylinder pipe l5. Chamber 5| communicates with the chamber 44 above the piston 31, when the piston 31 is in its normal position shown, through a branch passage 53 of the passage 52, the passage 53 containing a restriction or choke 54. Another branch passage 55 of the passage 52 opens into the bore 43 at a point immediately above the vent valve 33 when the vent valve 39 is seated on its annular rib seat 47.

The choke 54 is of such size that when fluid under pressure is supplied into the annular chamber 5| and thus to the brake cylinder II, in the manner to be hereinafter described, chamber 44 at the upper side of the piston 37 becomes sufliciently rapidly charged through the choke 54 that the spring 45 is effective to exert a suflicient force on the piston 37 to maintain the vent valve 39 seated on its annular rib seat 41. With the annular chamber 5| and brake cylinder charged with fluid under pressure, a sudden reduction of the pressure of the chamber 44, as by venting in the manner hereinafter described, creates a sufficient differential fluid pressure force on the piston 31 to cause it to be shifted upwardly against the yielding resistance of spring 45 until an annular rib 59 formed on the upper face of the piston 31 engages a portion of the gasket 33a between the casing sections 3| and 32, which serves as a gasket seat.

When the piston 31 is shifted upwardly into seated relation on gasket 33a, the vent valve 39 is shifted upwardly to a suflicient degree to establish communication between the passage 55 and The piston 37 operates in a suitable nular rib seat 12.

the. exhaust port 48 whereby fluid under pressure is rapidly released from the brake cylinder its normal position to its upper seated position on the gasket 33a, the piston. 31 passes the opening of the passage 53 into the chamber 44 and thus the chamber 44 at the upper side of the piston is isolated from the brake cylinder. Ac-

cordingly, as long as the chamber 44 is maintained vented, and the pressure in the brake cylinder II is effective to exert a suflicient force in chamber 5| on the lower side of the piston 31 to overcome the spring 45, the piston 31 remains in itsupper seated position. Spring 45 is of such strength that when the pressure in the brake cylinder acting to maintain the piston 31 in its upper seated position reduces to a certain uniform low pressure, such as five pounds per square inch, the spring becomes effective to shift the piston 31 downwardly to reseat the vent valve 39 on its annular rib seat 41 and restore the connection between the supply passage 56 and the annular chamber 5|. The reapplication control device. 35 comprise a valvepiston 6|, a valve 52 hereinafter called the sanding valve, and an exhaust valve 53, all of which are arranged to be operated by a piston 64.

The valve piston 6! of the reapplication control device 35 is guided in a suitable bore 55, formed in the casing section 32, and extends into a chamber 66 in the casing section 3|, which is constantly connected through another section of the brake cylinder pipe l5 to the straight-air pipe M. A suitable breather port 60 is provided in the valve piston 6| toprevent dash-pot action thereof. Separating the chamber 56 in the casing section 3| from another chamber 61 out of which leads the supply passage 56, previously referred to, is a wall 68 and communication between the two chambers through the wall is provided by a relatively large bore or passage 69 and a relatively small passage 1|] having a choke element H therein. An annular rib seat 12 is formed on the will 88 in surrounding relation to the bore '69, and the valve piston Si is adapted to seat on rib-seat'lZ to close communication through the passage 69 from the chamber 66 to the chamber 67, thereby restricting communication between the chambers to the passage 10 containing the choke element H. An annular gasket 13 is inset in the face of the valve piston 6| for effecting sealing engagement with the an- Interposed between the casing section 32 and the back side of the valve piston 6| is a coil spring 14 which'is efiective to urge the valve piston 6| downwardly toward seated relation on the annular rib seat 12.

The piston 64 operates in a suitable bore 15 in the casing section 3| and has a hollow stem 16, projecting to one side of the piston and closed at the outer end thereof, which stem operates in a suitable bore Tl that opens into the chamber 61 and is of smaller diameter than the bore 15. Formed at the outer closed end of the hollow stem 13 is a pin I8 which projects upwardly through the chamber 6? and passage 69 into the chamber 66 where it engages the seating face of the valve piston 5| within the annular gasket 13.

The bore 15 in which the piston 64 operates opens at the face of the casing section 3| covered by the casing section 33 and a chamber 19 is thus formed between the piston 64 and the casing section 33. I nterposed between the casing section 33 and the closed end of the hollow stem 16 of the piston 64 in the chamber 19 is a coil spring 8| which yieldingly urges the piston 64 upwardly to effect engagement of the upper end of the pin 18 with the face of the valve piston 6| and unseating of the valve piston 6| against the yielding resistance of the spring I4.

When the piston 64 is in its upper or raised position unseating the valve piston 6|, it uncovers the opening of a passage 83 into the bore 15 at the lower side thereof, which passage 83 is connected to the chamber 66 and has a restriction or choke 82 therein.

When the straight-air pipe I4 is charged with fluid under pressure, fluid under pressure is supplied therefrom through the one section of the brake cylinder pipe l5 to the chamber 65 and then past the unseated valve piston 6|, through the passage 69, chamber 31, passage 56, annular chamber 5|, passage 52 and the other sectlonof the brake cylinder pipe |5 to the brake cylinder H. supplied through the passage 83 to the chamber 13 at the lower side of the piston 64. Accordingly, since opposite sides of piston 34 are subject to opposing pressures, spring 8| maintains the piston 64 in its normal or raised position unseating the valve piston 6|.

Operation of the piston 64 downwardly is effected by a sudden rapidventing of fluid under pressure from chamber '19 at the lower side thereof resulting from unseating of the vent valve 39 of the release valve device 34. The outer seated area of the vent valve 39 within the bore 43 is connected to chamber 19 by a short passage 86 which opens into the bore 15 at a point adjacent the casing section 33. chambers 61 and 19 on opposite sides of the piston 64 are both charged with fluidunder pressure, the unseating of the vent valve 39 from its annular rib seat 41 vents fluid under pressure from chamber F9 at a rapid rate through the passage 88 and exhaust port 48. The higher fluid pressure in chamber 61 acting on the upper side of the piston 54 thus shifts the piston downwardly against the yielding resistance of the spring 8| and causes an annular rib 87 formed on the lower face of the piston 64 to engage in sealing relation a gasket seat formed on the gasket 33b between the casing sections 3| and 33. In shifting downwardly toward the gasket seat,

the piston 64 passes the opening of the passage 83 and thus cuts off the supply of fluid under pressure from the chamber 36 into the chamber 19 and transfers it to the annular chamber 88 at the upper side of the piston 64, so that the combined pressures of the fluid in chambers 61 and 88 are effective over the entire upper face of piston and the closed end of stem 16 to thereafter urge the piston positively into seated position on its gasket seat. The passage 85 opens into the bore 15 sufficiently close to the casing section 33 that when the piston 64 is seated on the seat portion of the gasket 33b, the passage 86 is not connected to the annular chamber but remains open to the'outer seated area beneath the piston.

The exhaust valve 63 isof the poppet type and is contained in a chamber 89 formed in the casing section 33. Valve 63 is yieldingly urged upwardly into seated relation on an associated valve seat formed on the casingsection33 by-a At the same time fluid under pressure is' Thus when the coilspring 9I interposed between the valve and a threaded plug 93 that is screwed into the outer open end of the chamber 89 and has a plurality of vent ports 92 therein. Valve 63 has a fluted stem 33 which is guided in a suitable bore connecting the chamber 89 and the chamber I9 at the lower side of the piston 64. .The end of the fluted stem 93 projects into the chamber 79 and is engaged by the piston 64, at a point within the annular rib 8?, so that when the piston shifts downwardly into seated position on the gasket seat of gasket 33b, valve 63 is unseated.

With the piston Gd'seated on its gasket seat and the exhaust valve 63 unseated, the chamber IQ at the lower side of the piston 64 is isolated and vented to atmosphere past valve 83 and through the vent ports 92 independently of the vent valve 39 of the release valve device 34. It will thus be apparent that with the lower face of piston 66 maintained subject to only atmospheric pressure, the fluid pressure in chambers G'I and 38 on the upper face of the piston is efiective to hold the piston in seated relation on its gasket seat thereafter as long as the force of the fluid pressure in chambers 51 and 88 is sufficient to overcome coil spring 8!. The area of piston 32 and the strength of coil spring 8| is such that once the piston is seated on its gasket seat, spring 8I is ineifective to unseat the piston upwardly from its gasket seat until the fluid pressure in chambers 67 and 88 on the upper face of piston 64 reduces below a certain uniform low pressure, such as five pounds per square inch.

The sanding valve 62 is a double beat valve and it is arranged to be normally urged into seated relation on an associated upper valve seat by a coil spring 94 and shifted downwardly against the yielding resistance of the spring 94 into seated relation on a lower valve seat when the piston 54 is shifted downwardly to seated relation on its associated gasket seat. The sanding valve 62 is contained in a chamber 35 to which the timing reservoir 24 is constantly connected, as by a pipe and passage 96, and is guidably supported by means of an annular flange 97 formed thereon which slidably engages in a suitable bore 98 in the casing. The flange 97 of the valve 62 is provided with suitable grooves 99 therein so that when the valve 82 is in its upper seated position, communication is established between a chamber IIBI, to which the sanding reservoir 22 is constantly connected as through a pipe I 02, and the chamber 95 whereby the timing reservoir 24 is charged to the pressure in the sanding reservoir 22.

The sanding reservoir 22. is constantly charged with fluid under pressure from the main reservoir l2, as through a branch pipe I03 connecting the main reservoir supply pipe 26 to the reservoir, a one-way or check valve I54 being interposed in the pipe N33 to prevent back flow of fluid under pressure from the sanding reservoir through pipe I03.

When the piston 54 is shifted downwardly into seated engagement on the seat portion of the gasket 33b it engages the end of a plunger I85 which in turn engages a lug I56 formed on the sanding valve 52 so that when the piston 64 is seated on its gasket seat the sanding valve 62 is shifted from its upper seated position to its lower seated position. The plunger I35 carries thereon a valve ID! of the poppet type, and a coil spring IE8 is interposed between the valve I! and the sanding valve 62 in a chamber I59 .for

yieldingly urging the valve I01 into seated position on an associated valve seat when the sanding valve 62 is in its upper seated position. When the valve I0! .is seated, it prevents leakage of fluid under pressure therepast througha bore H2 connecting the chambers 19 and H39 through which bore the plunger I35 extends. The plunger I05 is provided with a series of axially spaced piston ring flanges II I which closely .fit bore II2 so as to prevent leakage of fluid under pressure from the chamber I9 to the chamber I59 and vice versa, while valve I0! is unseated.

The sanding valve device 23 comprises a casing containing an operating piston H4 having at one side thereof a piston chamber H5, that is constantly connected to the chamber I09 of the control valve mechanism It as through a pipe and passage H6, and having at the opposite side thereof a chamber III whichis constantly open to atmosphere through a port I I8. open to atmosphere through a vent a choke H9 therein.

The piston N4 of the sanding valve device 23 is provided with a stem I2I which carries a valve I22 of the poppet type. The casing of the sanding valve device 23 has two spacedwalls I23 and I24 therein, the wall I23 having a central opening through which the stem I2I of the piston extends in close-fitting slidable relation to prevent leakage of fluid under pressure along the stem I2! from a chamber I25, formed between the walls I23 and I2 1, to the atmospheric chamber 'I H. The wall I24 has a port I26 which connects the chamber I to a chamber I27 that is port having constantly charged with fluid under pressure from the sanding reservoir 22, as by a branch pipe I 28 of the sanding reservoir pipe I52.

The valve I22 on the piston stem I2I is normally yieldingly urged in the right-hand direction, as seen in the drawing, into seated relation on an associated valve seat formed on wall l24 to close the port I26, by a coil spring I29 contained in the chamber I21 andv interposed between the valve I22 and the casing.

A plurality of the sanding devices 2| are connected to the chamber I25 of the sanding valve device 23, as by connecting pipes I3I.

It will accordingly be seen that when fluid under pressure is supplied to the piston chamber N5 of the sanding valve device 23, valve I22 is unseated and fluid under pressure is supplied therepast from the sanding reservoir 22 to the sanding devices 2% to effect sanding.

The magnet valve device I? functions to control the exhaust communication for the cham ber 44 at the upper side of the operating piston 31 of the release valve device 34 in the control valve mechanism It. Magnet valve device I1 comprises a suitable casing containing a valve I35 of the poppet type, and an electromagnet winding or solenoid I35 efiective, when energized, to actuate a plunger I31 which in turn unseats the valve I35 irom an associated valve seat against the yielding resistance of a coil spring I33. The valve 535 is contained in a chamber I39 which is constantly connected as through a pipe MI to the piston chamber 44 of the release valve device 34 in the control valve mechanism I6. Upon energization of the electromagnet winding I36 and unseating of the valve I35, communication is established past the valve 1 35 from piston chamber 44 and the chamber I39 to a chamber I32 which is constantly open to atmosphere through a port I43. Thus, as long as the electromagnet winding I36 .is energized,

Pipe I I 6 is "20 All) the chamber 44 'of the release valve device 34 is vented to atmosphere through the exhaust port I43 of the magnet valve device I1 and when the electromagnet winding I36 is deenergized the venting communication is closed.

The wheel-slip responsive device I8 is illustrative of any suitable device for effecting energization of the electromagnet winding I36 of the magnet valve device I1 instantaneously upon the slipping of a vehicle wheel with which it is assooiated. As shown, the wheel-slip responsive device I 8 is of the type described and claimed in my copending application Serial No. 137,956, filed April 20, 1937, now Patent 2,140,620.

Briefly, wheel-slip responsive device I6 comprises a tubular casing I45 in which is contained a rotary inertia element in the form of a flywheel I46, a driving shaft I 41 for the fly-wheel and a switch device I48. The driving shaft I41 is supported at opposite ends thereof by ball bearings I49, one of the bearings being contained in the end cover I5l of the casing I45 and the other being slidably supported within a bore I52 formed in the laterally projecting hub portion I 53 of the fly-wheel I46.

The fly-wheel I46 is supported for rotation within the casing by a ball bearing I54 at the end of the hub portion I53, which bearing is arranged to-move slidably in a bore I55 of the casing, and by another ball bearing I56 inset at the opposite end of the hub portion in a suitable recess formed in the face of the fly-wheel, which bearing is arranged to rotatably and slidably support the fiy-wheel on the shaft I41.

Suitably fixed on the outer end of the shaft I41 which projects through theend cover I5! of the casing is a pulley I6! having an annular groove I62 therein for receiving an endless belt that connects the shaft to any rotary element, such as the wheel axle, that rotates according to the rotation of one of the vehicle wheels on which the brakes are applied by the brake cylinder II.

'The fly-wheel I46 is rotated by rotation of the shaft I41 through a clutch arrangement compris ing a disc I63 fixed to the shaft, and a coil spring I64 so interposed between a collar or flange I65 on the shaft I41 and an annular shoulder I66 within the bore I52 of the hub portion I53 of the fly-wheel, as to urge the fly-wheel I46 and the disc I63 into interlocked or clutching engagement. Suitable thrust bearings I61 are provided for sustaining the axial thrust of the pulley I61 on the end cover I 5I due to the force of the spring I64 and also the thrust of the spring I64 on the fly-wheel I46.

The disc I63 and the fiy-wheel I46 are interlocked by means of a plurality of spaced pairs of complementary registering recesses I69 and I16, in the juxtaposed faces of the disc and flywheel, and a steel ball I1I in each pair of complementary recesses. Any suitable number of pairs of recesses I69 and I16 may be provided,

arranged in spaced circumferential relation-rat dially outward from the shaft I41,

The recesses I69 and I1Ilare relatively short and curved uniformly about the axis of the shaft I41, so. as to resemble somewhat the contour of a kidney bean, and vary in depth along the arc, thereof with respect to the face of the disc or fiy-wheel in which they are located, being deepest at the mid-point and sloping outwardly in opposite directionsto the face of the disc or fly-wheel.

, -It will thus be seen that under the influence of-spring I64 the steel balls I1I normally seat in the deepest portion of each pair of complementary recesses I69 and I16 so that the flywheel I46 and the disc I63 are accordingly normally interlocked for rotation together.

The compressive force or strength of the spring I64 is such as to maintain the fly-wheel! and hicle wheel and its 'associated rail' surface, that is, by slipping of the wheel.

When the shaft I41 decelerates'at a rate corresponding to the deceleration of the vehicle wheel while slipping, the fly-wheel I46 tends to over-run or lead the shaft I41'and consequently shifts rotatively forward of its normal position with respect to the disc I63. When the shaft I41 accelerates according to the rate of'acceleration of the vehicle wheel back toward a speed corresponding to vehicle or rail speed while slipping, the fiy-wheel I46 tends to under-speed or lag behind the shaft I41 and consequently shifts rotatively'backward of its normal position with respect to the disc I63.

In view of the steel balls I 1| interposed between the disc I63 and the fly-wheel I46, the rotatlve shift of the fiy-wheel I46 relative to the disc, either forwardly or backwardly of its'normal position, causes the fly-wheel I46 to be shift ed axially in the right-hand direction against the yielding resistance of the spring I64.

The degree of rotative shift of the fly-wheel I46 relative to the disc I63 is limited to a degree which prevents the steel balls I1I from leaving the complementary recesses I66 and I16, as by one or more pins (not shown) in the disc or fly wheel cooperating with arcuate slots and grooves (not shown) in the fiy-wheel or disc, in the manner shown and described in my above-mere tioned Patent 2,140,620.

The switch device I48 of the wheel-slip responsive device I6 comprises a pair of flexible resilient contact fingers I15 and I16, each of which is fixed at one end to aninsulating member I11 secured within the casing I45 at the end'o'f the hub portion I53 of thefiy-wheel. Thecontact fingers I15 and I16 are disposed in spaced parallel relation in alignment with the axis of the shaft I41, the free ends of the contact fingersbeing normally disengaged from each other. Whenthe fly-wheel I46 is shifted in the right-hand direction, as a result of shifting rotatively relative tothe disc I63, the closed end of the hub portion I63 of the fly-wheel engages the free end of a resilient spring member I18, fixed at its opposite end in theinsulating member I11 in alignment with the contact fingers I15 and I16, andbends'it laterally-against the contact finger I15 which is, in turn, bent intocontact with the contact finger I16. A tip I19 of insulating material is provided on spring member I18 for preventing the grounding of the contact fingers'l15 and I16 of the casing.

The pressure operated switch I9 functions jointly with theswitch device I48 of thewheelslip=responsive device I8 to control energization and' deenergization of the electro-magnet winding I36 of the magnet valve device I1: As shown diagrammatically, the pressure switch l9 comprises a casing having a piston It! for operating a switch member I82 into and out of contact with a pair of contact members I83, suitably carried in insulated relation on the casing. The switch member I82 is carried in insulated relation on a stem I 84 of the piston till, end a coil spring I85 interposed between piston i 8| and the casing yieldingly urges the piston l8! downwardly to a limit position in which the switch member I82 disengages the contact members Hi3. Formed in the casing at the side of the piston ls'i opposite the spring 885 is chamber l8fi which is con-- nected to the straight-air pipe i l at a point adjacent the brake valve l3 through a branch pipe I87.

The strength of the spring I35 is such that when the fluid pressure established in the straight-air pipe M and. effective in the chamber I86 on the piston it! exceeds a relatively low pressure, such as five pounds per square inch, the resisting force of the spring is overcome and the piston I8! is shifted upwardly to eifect en'- gagement of the switch member I82 with the contact members I83.

The electro-magnet winding I35 of the magnet valve device I l is energized by current supplied from a suitable source, such as a storage battery I89, which may be the storage battery for the lighting system on the cars of the train, under the joint control of the switch device 148 of the wheel-slip responsive device If and the pressure switch 19. The control circuit for the electro-magnet winding I36 needs no description for, as clearly seen in the drawing, the magnet winding I36, the switch device Hi8 of the wheel-slip responsive device i 8 and the pressure switch i9 are connected in series relation across the tor minals of battery I89.

Operation of equipment The main reservoir i2 is charged to the normal pressure carried therein, as from a fluid compress'or not shown, in the usual manner. The sanding reservoir 22 is charged to the pressure in the main reservoir l2 through the branch pipe I03 and the timing reservoir 24 is also correspondingly charged with fluid under pressure past the sanding valve 62 of the control valve mechanism 16 which is in its normal upper seated position.

Let it now be assumed that a car or train is traveling along the road under power or coasting and that the equipment is conditioned as shown in the drawing, thebrakes being released. To efiect an application of the brakes, the op erator first cuts off the propulsion power, if the power is on, and then shifts the brake valve handle 25 out of its normal release position into the application zone an amount corresponding to the desired degree of application of the brakes. The straight-air pipe [4 is accordingly charged with fluid under pressure from the main reservoir I 2 to a degree corresponding to the position of the brake valve handle in the application zone and fluid under pressure is accordingly supplied from the straight-air pipe I l through brake cylinder pipe I5, chamber 66 of the control valve mechanism It, past the unseated valve piston SI. passage 69, chamber 51, supply passage 56. annular chamber 5!, passage 52, and brake cylinder pipe l5 to the brake cylinder H. Accordingly, the fluid pressure established in the brake cylinder II corresponds to that established in the straight-air pipe M and the brakes are thus applied to a degree corresponding to the position of the brake valve handle 25. i

As long as the degree of'application of the brakes, as determined by the pressure in the brake cylinder H is not sufficient to cause slipping of the wheels with which the brake cylinder If is associated, the control valve mechanism it remains conditioned as shown in the drawing, and the operator may shift the brake valve'hsndie 25 as desired to correspondingly control the pressure in the brake cylinder to secure any desired degree of application of the brakes.

In the event, however, that a wheel on which the brakes are applied by the brake cylinder H begins to slip due to the application of the brakes, the wheel-slip responsive device Hl operates in the manner previously described to close its switch device 58 which complet'es'the circuit for energizing the electro-magnet winding I36 of the magnet valve device ll, it being understood that the pressure switch l9 has previously been actuated into circuit-closing position due to the pressure established in the straight-air pipe i l.

Valve [35 of the magnet valve device I1 is accordingly unseated to establish the exhaust passage for venting fluid under pressure from the piston chamber 44 above the piston 31, of the release valve device 36. Piston 31 is accordingly shifted upwardly into seated engagement on its gasket seat and the piston chamber M is accordingly disconnected from the passage 53 and isolated at atmospheric pressure. At the same time, the vent valve 39 is unseated upwardly to exhaust fluid under pressure from the brake cyl"- inder ll through the exhaust port 48, and the piston ll of the release valve device 34 cuts off communication from the supply passage 55 to the annular chamber Si and connected brake cyl inder II.

It will thus be seen that the release valve device 34 is operated instantly in response to the initiation of slipping of the vehicle wheels to cut oil the further supply of fluid under pressure to the brake cylinder H and to vent fluid under pressure at a rapid rate from the brake cylinder. Inasmuch as the chamber 44 above the piston 31 of the release valve device 3'3 is isolated at atmospheric pressure and brake cylinder pressure is efiective in the annular chamber 5| on the lower face of the piston 31, the piston is maintained seated on it's gasket seat until the pressure in the brake cylinder reduces below the relatively low uniform pressure of five pounds per square inch, as previously explained.

The vent valve 39 of the release valve device 3 1 is effective when. unseated to vent the chamber ls at the lower side of the piston 64 of the re application valve device 35, and accordingly the piston 64 is actuated downwardly into seated relation on the gasket 33b. The valve piston 61 is thus shifted into seated relation on the annular rib seat 12 to prevent the supply of fluid under pressure from the straight-air pipe 14 through the passage 69 to the chamber 6! and supply passage 56. Also, the exhaust valve v63 is unseated and the sanding valve 52 shifted from its upper seated position to its lower seated posi tion.

It will be apparent that the piston 64, in shifting downwardly to seated position on its gasket seat, passes the passage 83 and thus causes the straight-air pipe pressure to become efiective through the passage 83 in the annular chamber 88 on the upper face of the piston 64. At the same time, the isolation of the piston chamber I9 is effected by engagement of the annular rib 8! on the piston with the gasket seat and the unseated exhaust valve 63 maintains the piston chamber I9 at atmospheric pressure. Thus, as long as the pressure in the straight-air pipe thereafter effective in the annular chamber 88 on the upper side of the piston 34 exceeds the relatively low uniform value sufiicient to overcome the force of thespring SI, the piston 64 is maintained in seated engagement on its gasket seat. 1 With the sanding valve 62 seated on its lower valve seat, communication is cut off between the sanding reservoir 22 and the timing reservoir 24, and communication is established past the upper valve seat through which fluid under pressure is supplied from the timing reservoir 24 to the piston chamber H5 of the sanding valve device 23. The piston I I4 is accordingly shifted in the lefthand direction to unseat. the valve I22, which opens communication through. which fluid under pressure is supplied from the sanding reservoir 22 to the sanding device-2I', to cause sanding of the rails adjacent the slipping wheels as long as the valve I22 is unseated.

The time that the valve I22 isunseated is limited, however, due to the exhaust of fluid under pressure from the piston chamber I I5 at a restricted rate through the exhaust choke H9 in the pipe I I6. The capacity of the timing reservoir 26 and size of the choke '9 may be so related as to maintain the valve I22 unseated for any desired length of time, as for example, the length of time required to bring a car or train to a complete stop, or a shorter interval of time. In any event, when the pressure in the piston chamber I I5 is reduced sufficiently due to the escape of fluid under pressure through the choke H9, the spring I29 becomes effective to reseat the valve I22 and thus cut off the further supply of fluid under pressure from the sanding reservoir 22 to the sanding devices 2|, thus terminating the sanding of the rails.

Assuming that the retarding force on the slipping wheels is relaxed correspondingly to the rapid reduction in brake cylinder pressure, the

vehicle wheels cease deceleration and begin to accelerate back toward a speed corresponding to vehicle or rail speed when the brake cylinder pressure has reduced a relatively small amount from that which initiated the slipping. Since a slipping vehicle wheel accelerates very rapidly back toward vehicle or rail speed once it starts such acceleration, it will be apparent that the slipping vehicle wheels will return to a speed corresponding to vehicle or rail speed before the pressure in the brake cylinder II is reduced sufficiently to permit the spring 45 of the release valve device 3-I to actuate the piston 31 and vent valve 39 thereof downwardly to reseat the vent valve 39 and reestablish the supply communication to the brake cylinder II. It will thus be seen that reapplication of the brakes associated with a'wheel which hasv slipped is held off or prevented until the wheel has fully returned to vehicle or rail speed. In some instances, it may happen that the reduction of the retarding force on a slipping wheel is not effected correspondingly to the reduction in brake cylinder pressure and that a considerable amount of reduction in brake cylinder pressure is required before the retarding force is reduced. In such cases, the vehicle wheel may reduce to a relatively low speed while slipping, and thus the time interval between the initiation of slipping and the return to vehicle or rail speed may be greater. In order, therefore, to prevent the immediate and rapid restoration of pressure in the brake cylinder, in such instances, which might result in recurrence of slipping of the wheels, the reapplication valve device 35 functions to restrict the rate of resupply of fluid under pressure to the brake cylinder upon restoration of the release valve device 34 to its normal position.

It will be apparent that, since the piston 64 of the reapplication valve device 35 is maintained downwardly in seated position on its gasket seat, the stem 18 is retracted downwardly, and thus the valve piston BI is maintained seated to close communication through the passage 69. Thus, when the release valve device 34 is returned downwardly to the normal position .shown' in the drawing to reestablish the supply communication to the brake cylinder I I, fluid under pressure can be resupplied to the brake cylinder from straight-air pipe It only at the restricted rate determined by the size of the choke element 'II.

It will be seen that the reestablishment of the supply communication to the brakecylinder II tends to cause a reduction of the pressure in the straight-air pipe I4 due to the flow of fluid under pressure from the straight-air pipe through the choke I I and brake cylinder pipe I5 to the brake cylinder II. Accordingly, thebrake valve I3 functions automatically upon the restoration of the release valve device 34 to its normal position, to maintain the pressure in the straight-air pipe Id at a pressure corresponding to the position of the brake valve handle 25, so that the ultimate degree of pressure reestablished in the brake cylinder I I corresponds to the position of the brake valve handle 25. However, dueto the restricted rate of supply of the brake cylinder II through the choke H, the pressure in the brake cylinder II is restored at a slow rate and thus suflicient pressure to cause recurrence of wheel slipping is not reestablished in the brake cylinder before the slipping vehicle wheel returns fully to vehicle or rail speed.

For well known reasons, the engineman on a train reduces the degree of application of the brakes, as the speed of the car or train reduces in order to cause retardation of the train ata more uniform rate throughout the stopping distance. Accordingly, assuming that the operator shifts the brake valve handle 25 towards release position from the initial position in the application zone, it will be apparent that the pressure ultimately restored in the brake cylinder II following return of the slipping wheel to vehicle or rail speed will be less than that which initiated. the slipping of the wheel, thus further minimizing the possibility of recurrence of wheel slipping.

It will be apparent that once the wheel-slip responsive device I8 operates in response to the initiation of slipping of a vehicle wheel, the control valve mechanism I6 is thereafter unaffected by variations in. the rotative condition of a slipping wheel, .as when it ceases to decelerate and begins toaccelerate back toward a speed corresponding to vehicle or rail speed. When the vehicle wheel ceases to decelerate and begins to accelerate while slipping, the flywheel I46 of the wheel-slip responsive device I8 is returned momentarily to its normal position, in which the contact fingers H5 and H6 of the switch device Hill are separated, thus efiecting dee-nergization of the electro-magnet winding I36 of the magnetvalve device I 1. Due to the fact that the brake cylinder pressure efiective in the annular chamher 51 on the lower face of the piston 31 of the release: valve device 35- maintains the piston in seated relation. on its gasket seat, such momentary separation of the contact fingers H5 and I of the wheel-slip responsive device l8 is without effect. Furthermore, as long as the vehicle wheel is accelerating back toward a speed corresponding to vehicle or rail speed, while slipping, at a rate in excess of ten miles per hour per second. the contact fingers H5 and HE re main in engagement. Thus, while the vehicle is so accelerating, the valve E of the magnet valve device I! continues to establish the venting com munication for the chamber M above the piston 31' of the release valve device 3 3.

It will thus be seen that the wheel-slip responsive device It is" in the nature of a trigger mechanism which sets the control valve mechanism It into operation, the valve mechanism. 28 functioning automatically, once it is set into operation,

independently of further operation of the wheelslip responsive device it during any one slipping cycle.

In the event that a vehicle wheel should again I begin to slipupon reapplication of the brakes thereon in the manner previously described, the wheel-slip responsive device l8 again. operates to vent the piston chamber 44 of the release valve device 34 and cause the release valve device 34 to cut off the supply of fluid under pressure to the brake cylinder and vent fluid under pressure rapidly therefrom. Since in such case, the piston 64 of the reapplication valve device 35 is still in its lower seated position on the gasket seat, the

unseating of the vent valve 39 is inefiective to cause operation of the reapplication valve device 35. However, upon the subsequent reseating of the vent valve 39 following sufficient reduction of brake cylinder pressure, the reapplication valve device 35 is conditioned as before to restrict the rate'of resupply of fluid under pressure to the crease the degree of application of the brakes,

as desired, to hold the car or train on any grade that may be encountered in service.

When it is desired to release the brakes prior to again starting the train, the operator merely shifts the brake valve handle 25 to release position, thus completely venting fluid under pressure from the straight-air pipe l4 and connected brake cylinder II to atmosphere and efiecting the complete release of the brakes.

It will be apparent that when the pressure in the annular chamber 88, acting to maintain the piston 64 of the reapplication valve device 35 in its lower seated position on its gasket seat, is reduced sufiiciently due to the reduction of the pressure in the straight-air pipe Hi, the spring Bl becomes effective to shift the piston 64 upwardly to its normal position unseating the valve piston El from the annular rib seat '52 to restore the communication through the passage 59 between the chambers 66 and 61, thus restoring the.

valve mechanism IE to its normal condition for another operation thereof. When the piston 64 of the reapplication valve device 35 is shifted upwardly to its normal position, the exhaust valve 63 is reseated to cutoff the exhaust com munication for the chamber 79 and, at the same time, the sanding valve 62 is returned upwardly to its upper seated position restoring the charging communication between the sanding reservoir 22 and the timing reservoir, so that the timing reservoir 24 is again recharged to the normal pressure carried therein.

It will be apparent that if the wheel-slip rcsponsive device 53 is associated with a traction wheel and axle unit and excessivev propulsion force is applied to the traction wheel upon starting of the car or train sufiicient to cause racing thereof, the contact fingers I and I16 of the switch device 148 thereof will be shifted into engagement with each other. However, with the brakes released, the pressure switch I9 is in circuit-opening position. so that the closing of the switch device M8 under such condition is inefiective to cause energization of the magnet winding I38 of the magnet valve device l1. Unnecessary consumption of current from the battery ass is thus avoided.

In the case of a train brake equipment, it should be understood that the difierent brake cylinders along the length of the train on the various cars are controlled by equipment duplieating that described for the brake cylinder II and, therefore, while the brake valve 13 is efiective under the control of the operator to control the application and release or" all the brakes th oughout the train, the various control valve mechanisms l6 and sanding valve devices 23 local to each brake cylinder, are automatically controlled to provide individual control of one or more wheel and axle units in response to the slipping of the wheels thereof.

Summary Summarizing, it will be seen that I have disclosed a fluid pressure brake equipment for" vehicles, such as railway cars and trains, operative to prevent sliding of the vehicle wheels. The

invention comprises essentially a control valve mechanism including a release valve device, a reapplication valve device, and a sanding valve adapted to be set in operation by a suitable wheel-slip responsive device in response to the initiation of slipping of. the vehicle wheels. The release valve device functions automatically to cut off the supply of fluid under pressure to the brake cylinder and to rapidly vent pressure from the brakecyilnder and to continue to vent fluid under pressure from the brake cylinder as long as the pressure therein exceeds a certain uniform low pressure such as five pounds per square inch. The reapplicatio-n valve device is automatically operated in response to the operation of the release valve device to prevent more than a restricted rate of resupply of fluid under pressure to the brake cylinder when. the release valve device is restored to its normal condition, The reapplication valve device is automatically held in its rate restricting position, once it is operated thereto, until the brakes are released.

The sanding valve is operated by the reapplication valve device to initiate sanding of the rails, the sanding being automatically timed to terminate after a certain uniform time, preferably sufficient to bring the train to a complete stop.

While I have illustrated and described only one embodiment of my invention, it will be apparent that various omissions, additions, or modifications may be made therein l without departing from thespiritpf my invention. For sexample; it will be apparent that, the sanding valve "62 of'the control valve mechanism l6 may bexomitted, if

the sanding operation is not desired.

Having now -.described my invention, what I claim as new and desire to secure by Letters Patent, is:

1. In a vehicle brake equipment of the type having a communication through which fluid under pressure is supplied'to effect application of the brakes and from WhiChzfiUid under pressure is released to effect release of thebrakes,.in combi? nation, a movable abutment having .a normal sanding when the said abutment is operated to.

its said different position. i 2. In a vehicle brake equipment of the type having a communication through which fluid under pressure is supplied to effect application of thebrakes and from which fluid under pressure is released to effect release of the brakes, in combination, a movable abutment having a normal position in which it is subject to the pressure in the communication and operatively unresponsive thereto, means effective upon the initiation of slipping of a vehicle wheel for rendering the said abutment responsive to the pressure in the said communication whereby said abutment is operated from its normal position to a different position, a rail sanding device, and means operated in response to the shifting of the said abutment to its said different position for effecting a supply of fluid under pressure to said sanding device to effect sanding of the rails.

3. In a vehicle brake equipment of the type having a communication through which fluid under pressure is supplied to effect application of the brakes and from which fluid under pressure is released to effect release of the brakes, in combination, a movable abutment having a normal position in which it is, subject to the pressure in the communication and operatively unresponsive thereto, means effective upon the initiation of slipping of a vehicle wheel for rendering the said abutment responsive to the pressure in .the said communication whereby said abutment is operated from its normal position to a different position, a rail sanding device, means operated in response to the shifting of the said abutment to its said dilferent position for effecting a supply of fluid under pressure to said sanding device to efiect sanding of the rails, and means effective to cause interruption of the supply of fluid under pressure to the said rail sanding device a certain uniform time after the said 4. In a vehicle brake equipment of the type having a communication through which fluid under pressure is supplied to effect application of the brakes and through which fluid under pressure is released to effect release of the brakes, in combination, a movable abutment having a normal position in which it is subject to opposing relation to the pressure in the communication and in a chamber that is charged with fluid under pressure from thecommunication whereby said abutment" is .-'-normally '1 unresponsive to -the. pres :sure in the communication; means for effecting a" sudden rapid reduction of? the pressure in said chamber. in response to. the initiationdf slipping of the vehicle wheels to render .theisaid abutment responsive to the pressure inthe communication and cause it to be-actuatedfromritsnormal-position to a different position, said abutment being so constructed and. arranged that when in its said different position it isolates .thersaid'chamher from the said communication and'maintains a reduced pressure in 'saidchamber whereby "the pressure in the communicationcis effective to maintain the abutment in its said different 'posi tion thereafter as long asthe'pressure inthe'com munication exceeds a. certain uniform pressure, a-.-rail sanding :device; asource of fluid under pressure, and valve'means operated in: response "to the operation of the said-abutment to its said different-positionto establish communication through which fluidunder pressure is sup-:

plied from the said sourcetto the-rail sanding device to effect sanding.

5.x'In a vehicle brake equipment'ofthe type having a communicationthroughwhich fluidunder pressure is supplied .to effect application of thebrakes and through whichfluidunder pres-'- sure released to effect release --of the brakes, in combination, a movable abutment having a normal position in which it is subject in'opposing relation to the pressure in the communication and in a chamber that ischarged with fluid under pressure from the communication whereby normal positiontoa different position, saidabut ment being .so constructed and arranged that when in its said difl'erent position itisolates the said chamber from the said communication and maintains: a reduced pressure inlisaidchamber different position thereafter as long as the pressure in the communication exceeds a certain uni-' form pressure, a rail sanding device, a source of fluid under pressure, valve means operated in response to the operation of the said abutment to its said different position to establish communication through which fluid under pressure is supplied from the said source to the rail sanding device to effect sanding, and means for causing the last mentioned valve means to interrupt the supply of fluid under pressure from said source to the rail sanding device, to cause cessation of sanding, a certain uniform time after the said abutment is shifted to its said different position.

, 6. In a vehicle brake equipment of the type having a communication through which fluid I under pressure is supplied to effect application abutment is shifted to its said different position.

of the brakesand from which fluid under pressure is released to effect release of the brakes, a

valve operative from a normal position in which it permits the flow of fluid under pressure through the communication at an unrestricted rate to a different position in which it permits the flow of fluid under pressure through the communication at only a restricted rate, a movable valve to its said different position,a rail sanding device, and means operative in response to the operation of said abutmentto its said difl'erent position to efiect'operation of said rail sanding device to effect sanding.

7. In a vehicle brake equipment of the type having a communication through which fluid under pressure is supplied to eifect application of the brakes and from which fluid under pressure is released to effect release of the brakes, in combination, a valve having a normal position which permits theflow of fluid under pressure through the communication at a relatively une restricted rate and a different position in which it permits the flow of fluid under pressure through the communication at a relatively restricted rate, a movable abutment having a normal positionin which it is effective to maintain said valve in its normal position, means effective upon the initiation of slipping of a vehicle wheel for causing operation of said abutment to a different position to effect operation of said valve to its said difierent position, means effective when said abutment is operated to its different position to maintain it in its different position thereafter as long as the pressure in the said communication exceeds a certain uniform pressure, a rail sanding device, and means operated in response to the operation of said abutment to its different position to cause said rail sanding device to eifect sanding.

8. In a vehicle brakeequipment of the type having a communication through which fluid under pressure is supplied to effect application of the brakes and from which fluid under pressure is released'to efi'ect release of the brakes, in combination, a valve having a normal position in which it permits the flow of fluid under pressure through the communication at a relatively unrestricted rate and a different position in which it permits the flow of fluid under pressure through the communication at a relatively restricted rate,'a movable abutment having a normal position in which it is effective to maintain said valve in its normal position, means effective upon the initiation of slipping of a vehicle wheel for causing operation of. said abutment out of its normal position to efiect the operation of said valve to its said different position, means operative in response to movement of said abutment out of its normal position for efiecting sanding, and means effective automatically to cause cessation of sanding a certain uniform time after the said abutment is operated out of its normal position.

9. In a vehicle brake and sanding equipment, in combination, means providing a communication through which fluid under pressure is supplied to effect application of the brakes and through which fluid under pressure is released to effect release of the brakes, a movable abutment subject on one side to the pressure in the communication and having a certain positionin which it is normally unresponsive to the pressure in the communication, means for rendering said abutment responsive to the pressure in the communication so that the abutment is moved out of, its said certain position to a different position in response to the pressure in the communication, a sanding device, and means operative in response to the operation of said abutment to its said different position for causing said sanding device to effect sanding. i

. 10. In a Vehicle brake and sanding equipment, in combination, means providing a communication through which fluid under pressure is supplied to effect application of the brakes and through which fluid under pressure is released to effect release of the brakes, a movable abutment subject on one side to the pressure in the communication and having a certain position in which it is unresponsive to the pressure in the communication, means effective upon the initiation of slipping of a vehicle wheel for rendering the said abutment responsive to the pressure in said communication so that said abutment is operated out of its certain position to a different position in response to the pressure in the communication, a sanding device, and means operative in response to the operation of said abutment to said different position for causing said sanding device to effect sanding.

CLYDE C. FARMER. 

